Refactor to reduce/improve use of stringstreams

[marcosbento]

Description

Refactor to reduce/improve use of stringstreams

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

🌦️ >> Documentation << 🌦️
https://sites.ecmwf.int/docs/dev-section/ecflow/pull-requests/PR-297

[codecov-commenter]

Codecov Report

❌ Patch coverage is 38.90977% with 650 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.63%. Comparing base (5466b43) to head (c988f0f).
⚠️ Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
libs/base/src/ecflow/base/cts/user/AlterCmd.cpp	21.60%	98 Missing ⚠️
libs/attribute/src/ecflow/attribute/RepeatAttr.cpp	25.00%	69 Missing ⚠️
libs/node/src/ecflow/node/EcfFile.cpp	34.14%	54 Missing ⚠️
libs/node/src/ecflow/node/Defs.cpp	41.17%	20 Missing ⚠️
libs/node/src/ecflow/node/Submittable.cpp	9.52%	19 Missing ⚠️
...bs/base/src/ecflow/base/cts/user/EditScriptCmd.cpp	0.00%	18 Missing ⚠️
libs/node/src/ecflow/node/TaskScriptGenerator.cpp	0.00%	18 Missing ⚠️
libs/base/src/ecflow/base/cts/user/ForceCmd.cpp	30.43%	16 Missing ⚠️
libs/base/src/ecflow/base/cts/user/CFileCmd.cpp	12.50%	14 Missing ⚠️
libs/base/src/ecflow/base/cts/user/LogCmd.cpp	0.00%	12 Missing ⚠️
... and 79 more

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #297      +/-   ##
===========================================
+ Coverage    49.54%   49.63%   +0.09%     
===========================================
  Files         1237     1237              
  Lines        98311    97566     -745     
  Branches     14844    14833      -11     
===========================================
- Hits         48704    48427     -277     
+ Misses       49607    49139     -468     

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